Process for obtaining pure copper.



LUOIEN'JUMAU, OF PARIS, FRANCE.

rnocnss on OBTAINING PURE, COPPER.

Specification of Letters Patent.

Patented April 21,- 1908.

T all whom it may concem:

Be it known that I, LUCIEN JUMAU, citizen of France, residing at Paris, in the said Hepublic, have invented new and useful Improvements 111 Processes for Obtainu'lg Pure Copper, (for which a French patent has been filed March 20, 1906,) of is a specification.

- My invention relates to an improved process for obtaining pure metallic copper from a solution of salts of copper, and it consists in which the following the steps and processes herein describedandclaimed. p

In the usual Wet method of extracting'copper from its ores, the ores, with oraaitlieut'...

previous roasting, are leached with a suitable solution for dissolving the copper; in the o eratlon of my invention, I prefer to emp oy an ammoniacal leaching solution.

- By my improved process, the solution containing salts of copper is treated witha suitable sulfite, such as, for exam do, a normal or acid sulfite of ammonia, or sulfite of hydrogen, commercially known as sulfurous acid; heat being referably employed during such treatment or the pur ose of Jprod-ucing amore compactand less iydrate recipitate. A precipitate so produced contains cuprous sulfite, occurring in the form of a cuprosocupric sulfite, or a double ammonium salt, or a mixture of said compound. As a matter of economy, the sulfurous acid used in this first step may be produced by the roasting of the eu rilerous ore, if the latter happens to be a su fid ore; ifammonium sulfite is to be used, this is readily made by passing a current of sulfurous acid into ammonia.

The precipitate obtained as aforesaid is separated from the liquid, which may be used for lixiviating a fresh batch of ore, either directly or after it has beenregenerated; for instance, if the lixiviating solution is to be ammoniacal, the dissolved sulfurous acid may be eliminatedand the a propriateuantity of ammonia added, '1 1e cost of t e ammonia is always low because the gas is easily regenerated from the solutions by treating, them with lime, baryta or magnesia, all of which frequently occur in the gangue of copper ores. A portion of the copper contained -m the precipitate is then obtained in a metallic state b treating said precipitate with anacid whic 'willc'ombine such as su luric acid. The fine may be stated as lollows:

Cu S0 use, Cu cuso, so, i 1 0.

The metallic copper is separated from the solution; the latter still contains copper and may be treated in the same manner as the original solution, that is to say, so as to obtain a precipitate of cuprous suliite. it is preferable, however, iirst .to enrich it in copper,either by e\-'aporation or l'iycmploying the solution for lixiviating a fresh quantity of ore.

The two treatments for obtaininp the precipitate of cu prous sulfite and that of copper, may succeed each other in a continuous manner, with very small cost of sulfurous acid, since the latter is regenerated in accordance .with the foregoing equation.

The metallic copper having been washed maybe melted directly to ingots or made into briquets by powerful compression. it may be treated, if necessary, by ordinary 'metallurgical or electrical refining methods, and the process according to this invention may be completed usefully by a very simple electrolytic refining of the precipitated copper obtained as described. For this purpose operation hydraulic press, so as to form anodes of suitable sha eand dimensions, or so as to coat eleotrica ly conducting supports of lead, carbon, copper or the like, muclias is practiced coating may also be performed byhand. The lates thusmade are used as anodes in an eectrolytic refining bath, the cathodes consisting of conducting supports such as are ordinarily used, while the electroiyicniay be, for example, the initial neutral, acid or basic solution of copper.

' The process just described may advantageous y be varied in certain cases as fol lows: lnstead .of treating as aforesaid the whole .of the cuprous sulfite precipitate to obtain metallic copper, only a part may be treated, or the treatment may be entirely avoided by operating in the following man- Iter. Theanodes are made from the euprous sulfite ora mixture of the sullite and the metallic copper. One of the most advantageous methods is to make a support from the co eris com )ressed for instance hr at v coatingthe plates of accumulators; this lill - the preci itated copper by means of the press, an to coat 'th1s support'with the precipitated cuprous' sulfite by pressure.

In the electrolysi-s'conducted as herein before described, there is obtained a deposit of pure copper ,on' the cathode with an. economical ex enditure of electricity the potential at t e'terminals of the'vat may be very nearthat which obtains in the electrolytic refining of copper, say from 0.2 to 0.5- volt. The reason for this low voltage is that during the electrolysis the SO, ions which arrive at the anode transform a molecule of cuproussulfite into a molecule'of copper and a moleculeof sulfur dioXid, so that thereis no liberation of oXygen'atthe anode.

To illustrate the succession of operations 1 for obtaining, by the application which has just been described, pure copper from its -ores, .the following example may be given as applied to suliid ores.

The mineral is roasted, then lixiviated with the ammonithe reaction being:

acal solution of ammonium sulfate. After having expelled from the solution the free ammonia which is to be used in a subse uent lixiviation, the sulfitization process fol ows,

In this solution in presence of the preci itated cuproso-cupric sulfite, a second mo ecule of sulfuric acid is added and heat applied; There is thenproduced the reaction:

Thus a third of the total copper is precipitatedas pure copper, and at the same time two-thirds of the sulfurous acid are regen-V erated which are utilized for a subsequent sulfitization; The sole cost in this case consists of a molecule ofsulfuric acid per mole- -molecu ed bylime or lixiviated ore yield back the 4 molecules of ammonia according. to the 'reacf I cule of copper. Even this, cost maybe avoided, as will presently be seen. The solution above the preci itated ure copper, containing the two mo eculeso copper sulfate receives the-free ammonia of a preceding operation and also a quantity of ammonia corresponding with the equati.on.

It may be remarked that thisammoniacosts' for there are produced two new nothing es of ammonium sulfate which treattion 7 I I 2CaSO +4NH +2H Q After the-addition of ammonia, the solution of lixiviation'difiers from the initial solution ticallynothing for materi I i 4 p n i Y- merely in that it contains two more molecules of ammonium 'sulfate'and two molecules of cop er oXid already dissolved. This solutibn being returned to the roasted ore redissol ves the third molecule of copper and .is'then subjected to sulfitization as in the first case. 'When thesolution becomes too rich in' ammonium sulfate, the latter is withdrawn, in] the form of crystals, for exam le, and treated, as indicated above, with EH18. y v

The sulfuric acid necessary for the preparation of the copper as has been said above '(Equation '2)-may be obtained by oxidizing a part of the sulfurous acid, either in lead chambers or by the contact process. But there are means for avoidingthis cost of sulfuric acid by operating in the following manner:Instead of regenerating all the ammonia by lime according to Equation (4), a part ofit may be obtained by simply decomposing the ammonium sulfate by heat, pro ucing ammonium bisulfatein accordance with the equation z 5 2(NH;,),SO, znrariso, ZNH When it is thus necessary, as has been seen,

to dispose of 4 molecules of ammonia for regenerating the solution of lixiviation, the t yo other molecules are derived lrom the tre ttment of a single molecule of ammonium sulfate with the lime or thelixiviated mineral,

according to the equation r (4/) (NH SO CaO OaSO,' 2NH H O.

As the two molecules of ammonium bisulfate,they may be. substituted for the molecule of sulfuricacid in the operation of transformingthe sulfite into cop er (Equation 2) which. then happens accor ing to the equation zcuso, Cu NH,, ,so, 211,0 2so,.

The sole difference from the case of treat.- ing with sulfuric acid is that there is here formed in solution a molecule of ammonium sulfate, which must be added to the two molecules that are derived as previously from the reaction: I

(3 201160, 4NH +4H During there'generation ofithelixiviation treating said cuprous sulfite with an acid tosaid solution with a in salts of copper, which consists in treating said solution with a sulfitefor producing a preci itate containing cuprous sulfite, and reduce a portion thereof to metallic co per.

2. The 'herein described process or obtaining pure copper from asolution containing salts of copper, which consists in treating sulfite for producing a precipitate containing cuprous sulfite, .and

treating said cuprous sulfite with sulfuric acid to reduce a portion thereof to metallic copper.

3. The herein described process for obtaining pure copper from a solution containing sa ts of copper, which consists in treating sai solution with sulfurous acid for producing precipitate containing a cuprous sulfite, and

7 treating said cuprous sulfite with an acid to .saidsolution with reduce a portion'thereof to metallic icotpper. 20. or oh- .4. The .hereindescribed process taining pure copper from a solution containing sa ts of copper, which consists in treating a sulfite for producing a precipitate containing cuprous sulfite, treating said cuprous sulfite with an acid to reduce a portion t ereof to metallic copper, forming said metallic copper. into suitable anodes, and subjecting said anodes to an lytic refining process.

electro- '5. The herein described process for obtaining pure copper from a solution containing salts of copper,.whichconsists in treating said solution with sulfurous acid for produc-. ing a precipitate containin treating said cuprous sul te with sulfuric acid to reduce a portion thereof to metallic co per, forming said metallic cop er into suitable anodes, and subjecting said anodes to an electrolyticrefinin process.

6. The herein described process for ob.- taining pure copper from a solution containin salts of copper, which consists in treating said solution. with a sulfite for producing a recipitate containingcuprous sulfite, reducin a portion of said cuprous sulfite to meta lic copper by treating it with an acid,forming said metallic copper and the unreduced portion of odes, and sub ect1ng said anodes to an electrolytic refining process.

In testimony whereof I have signed my name to thls'specification in the presence of 7 two subscribing witnesses.

LUCIEN JUMAU.

Witnesses J ULES FAYoLLEr, EUGENE PICHoM.

cuprous sulfiteinto suitable an- 

